The latest technology knows systems that capture the EEG with suitable electrodes at predefined standardized positions and feed it to an amplifier. The disadvantageous effect is that the electrical activity can only be captured from relatively large areas of the brain.
But in many medical problems of neurology, physiology or the function diagnostic the local brain activity of certain anatomical limited areas or centers is of more essential significance. A series of extensive signal processing steps is necessary to capture the electrical activity of such areas and to free them from disturbances by the adjacent brain areas. For that the amplified EEG must be digitalized and afterwards analyzed in a computer.
One disadvantage of this procedure is that only an offline analysis is possible. Therefore, this procedure can not be used in time critical procedures either.